Tailored bio-based carbon materials

Introduction

Carbon is an old material utilized by people since prehistoric era and their importance has increased over the time. In last century new carbon materials with tailored properties has been developed, including e.g. strong carbon fibres for composites. In recent decades even more sophisticated nanosized carbon materials have been produced. While nanocarbon materials are typically prepared in gas synthesis methods, macroscopic carbon materials are usually prepared by carbonization of suitable solid precursors. These precursors can have various shapes and dimensions depending on the application field including particles, fibres and wires, sheets and fabrics, and spatial objects such as 3-D fabrics and foams. Carbonization process and conditions also have major impact on properties of carbon including crystallinity, porosity, purity and functionality. Some carbon is also lost during carbonization processes (volatile carbon), so the yield depends also on carbonization process.

Carbon materials are being intensively studied all over the world at the moment. The drivers for the novel materials and processes nowadays come from sustainable development, energy efficiency and green solutions. Bio-based carbon materials can in the future form the basis of markets currently dominated by petroleum-based carbon materials. Our approach is to use renewable wood polymers as raw materials for solid precursors which can be carbonized into novel structural carbon materials to meet the requirements of selected added value applications.

This work is carried out within a project funded by Tekes (the Finnish Funding Agency for Technology and Innovation). The aim is to survey technological possibilities to obtain lignocellulose-based high performance structured carbon business in Finland. In this work we review our raw material options and precursor preparation methods, as well as carbonization processes. We have used two different carbonization processes - hydrothermal carbonization (HTC) and high-temperature carbonization – producing different kind of materials.